Method of coating articles with enamel



June 10,; 1930. N. B. ORNITZ METHOD OF COATING ARTICLES WITH ENAMEL ori inal Filed Sept. 17, 1926 -INVENTOR.

wrm Q ATTORNEYS Patented June 10, 1930 UNITED STATES PATENT OFFICE.

NATHANIEL I B. ORNITZ, F PITTSBURGH, PENNSYLVANIA, AS SIGNOR TO THE BAB- COCK & WILCOX TUBE COMPANY, OF BEAVER FALLS, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA METHOD OF COATING ARTICLES WITH ENAMEL Application filed. September 17,1926, Serial No. 136,041. Renewed October 12, 1929.

My present invention relates to methods of enamelling metal objects, particularly long ones, such as rods and tubes, and more particularly by a substantially continuous process. Preferably the enamel is vitreous from the following'description and the .an-

nexed drawings, in which Fig. l is a side elevation, partly in section, of an apparatus suitable for carrying outmy improved method, such view being more or less dia grammatic; Fig. 2 is a-view of a connector used in my novel method; Fig. 3 is an enlarged section of one of the details of Fig. 1, and Fig. lis a view more or less diagrammatic of another piece of apparatus which may be used in practicing my invention.

Like reference characters indicate like parts in the several views.

For illustrative purposes, I have shown an apparatus for racticing my invention in enamelling of tie exteriors of long tubes of relatively small diameter, say'2 inch tubes 20 feet long, with vitreous enamel, though it will be understood that my invention is not limited to the illustrative embodiment. A

In using the apparatus shown, the tubes, are first sand-blasted to clean the surface thoroughly and then the enamel in fluid form is applied in the usual manner, so that the surface of the metal is coated with either one or two coats as may be desired.

Preferably the enamel is air-dried on the tube before the baking operation, and it inay also be dried in a similar manner between the successive applications of the fluid enamel. For this purpose, the tube T may be conveniently supported on books or tubes 8, 9, inserted into the ends of the tube T, the

tube 8 providing an air jet by which warm air may be blown to dry the enamel. The tube being supported in the manner indi ca'led, the enamel coating is not injured.

After the coating-is sufficiently dried, the tube is laid on a traveling carrier: 10 in Fig.

1, the surface of the carrier preferably being made up of a relatively hard felt forming a' kind of cradle so as not to mar the still unbaked enamel. The carrier 10 leads toward .the furnace 11 which may. be heated in any suitable manner, as by the gas jets shown.

The furnace 11 has a muflle 12, say, of carborundum, extending across the furnace and in alignment with openings 13 and 14 in the furnace walls which are relatively small but large enough to permit the tube T topass through them without contact.

-.A tube to be enamelled is laid on the carrier 10 and the carrier moved so that the tube is first carried through the hole 13, then through the muflle 12 and out of the hole 14. onto a carrier 15, the rate of travel of the carriers 10 and 15 being slow enough to .'permit a thorough baking of the enamel during the passage of the tube throughthe muflle 12.

It will be obvious that the forward end of the tube is subjected to .the i nten se baking heat while it is unsupported by a carrier and that similarly, the rear end of the tube is heated while unsupported 'by a carrier,

unenamelled dummytube which is connected to the front end of the first enamelled tube by a connector, such as 16, shown best in Fig. 2, this connector, in the form shown, being merely a shell preferably having a projecting rim 17, the diameter of the shell being such that it fits more or, less loosel into the ends of the tubes being enamelle It will be noted, therefore, that the dummy tube can be carried through the furnace and it will be immaterial whether its forward end sags or not, but the rear end will support the front end of the first tube T, so that this front end will not sag. Thereafter, the tubes are carried through the furnace one after the other, the rear end of one tube being connected to the forward end of another tube by a connector 16. Consequently there is, in efiect, a continuous flow of tubes through the furnace with their ends so connected as to form, in effect, a continuous tube, so that both ends of each tube are supported at all times and the sagging of these ends prevented. At the end of the operation, a dummy tube will be connected to the lastcoated tube to prevent sagging ofthe end of the latter.

It will be understood that, after the tubes are finished, the connectors 16 are removed and used over again at the right-hand side of Fig. 1.

Notwithstanding the continuous natureof the operation described above, the tubes are necessarily unsupported between the ends of the carriers 10 and 15 and, because the enamelled surface ought not to be touched while highly heated, it is undesirable to place any supports in the furnace. Consequently the weight of the tube is sufficient to cause a sagging of the heated tube which would result in a bent tube. To overcome this, I apply, a jet of air throu h the pipe 19 against the upper part of t e hot tube T as it emerges from the furnace 11 and regulate this blast of air so that the chilling of the upper surface is just enough -to straighten the tube and restore it substantially to its original condition of straightness.

The tube T, after passing the straightening point, passes through a cooling jacket 20,-the preferred construction of which is illustrated in cross-section in Fig. 3. The jacket 20 is provided with-an air space 21 by means of a pair of horizontal sleeves 22 and 23, the latter being threaded into the end of the jacket 20.

In the construction described, the air enters the space 21 from the pipe 24 and emerges through the circumferential crack or slit 25, the width of which can be regulated by turning the sleeve 23 in its threaded connection to the jacket 20. v

With this arrangement, a blast of air is directed through the crack 25 against the entire circumference of the hot enamelled surface emerging from the furnace, so-that the-enamel is chilled and hardened before the finished tube touches the carrier 15.

It w1ll be understood that the apparatus for carrying out my method may be widely varied. Any form of enamel which is usually baked on metal surfaces may be used,

- and, while I have illustrated my invention particularly in connection with the enamellmg of tubes, it will be readily understood that many of the features of my invention may be employed in the enamelling of other objects, particularly those of considerable length. It will also be noted that with the apparatus shown the article being enamelled s never supported on points or the like during the time .when the enamel is being fused on the iron. Indeed, the only time when'the unfinished tube contacts with a support is when the air-dried enamel rests on the felt meaaae surface of the carrier 10, and at this time a slight contact with the enamel surface-does and baking of the article done when the article is in a horizontal position, there is little or no tendency for the enamel to flow.

It will-also be understood that the invention is not limited to the use of the particular form of furnace which I have chosen for purposes of illustration, since any furnace may be used and even the muflie 12 may be dispensed with, though preferably it is used to prevent the heating gases from in uring the enamel.

It will also be understood that the form of connector which is used will be dependent on the character of the article, it only being necessary to provide such a connector that when an article being finished is in the furnace, its ends will find support from the preceding and succeeding articles which are respectively finished or to be finished by passage through the furnace.

I claim: 7

1. The method of enameling long articles which consists in coating the articles with fluid enamel and then moving the articles endwise slowly into and out of a furnace while supporting the article outside the furnace only.

2. The method of enameling articles which consists in coating a plurality of the articles, connecting them together temporarily end to end, and moving the connected articles slow endwise into and out of a furnace while supporting them outside the furnace and keeping them free from contact with any part within the furnace.

3. The method of enameling articles which consists in coating a plurality of the articles, connecting them together with temporary connectors which are out of contact with the coated surfaces, and moving the connected articles slowly into and out'of a furnace while supporting them outside the furnace and keeping them free from contact with any part within the furnace.

4. The method of enameling articles which consists in coating a plurality of the articles, connecting them together with temporary connectors which are out of contact with the coated surfaces, moving the connected articles slowly into and out of a furnace while supporting them outside the furnace and keeping each article free from contact with any part within the furnace, and chilling the fused enamel on each article before it is touched by a support outside the furnace.

5. The method of enameling tubes, which consists in coatin the exterior of the tube with enamel, an

thereafter moving the tube endwise through a heating zone while maintaining the highly heated surface free from contact with any part of the heating apparatus.

6. The method of enameling tubes which consists in coating the exterior of the tubes with fluid enamel, moving the tube slowly endwise through a furnace while supporting it outside the furnace and keeping it free from contact with any part within the furnace, chilling the fused enamel on the-tube as it emerges from the furnace and before it is touched by a support.

7. The method of enameling tubes which consist in coating the exterior of the tubes with fluid enamel, moving the tube hori- 1 zontally and slowly endwise through a furnace while supporting it outside the furnace and keeping it free from contact with any part within the furnace, chilling the fused enamel on the tube as it emerges from the zontallyand slowly endwise through a furnace while supporting them outside the furnace and keeping them free from contact with any part within the furnace, directing a stream of relatively cold air orgas against the upper surface. of each tube as it emerges from the furnace and while it is hot, to

straighten it, and then chilling the fused enamel around the entire circumference of each tube before the enamel is touched by a support.

NATHANIEL B. ORNITZ.

furnace and before it is touched by a suport.

8. The method of enameling tubes which consists in coating the exterior of the tubes with fluid enamel, moving the tube horizontally and slowly endwise through a furnace whilesupporting it outside the furnace and keeping it free from contact with any 7 consists in coating the exterior of 'a plurality of tubes with fluid enamel, connecting the tubes-temporarily end to end by connectors,

' .moving the connected tubes slowly endwise through a furnace while supporting them outside the furnace and keeping them free from contact with any part within the furnace, chilling the fused enamel on the tubes as they emerge from the furnace and before the enamel is touchedby a support.

10. The method of enameling tubes which consists in coating the exterior of a plurality of tubes with fluid enamel, connecting -.the tubes temporarily end to end by connectors, moving the connected tubes horizontally and slowly endwise through a furnace while supporting them outside the furnace and keeping them free from contact with any part within the furnace, chilling the fused enamel on the tubes as they emerge from the furnace and before the enamel is touched by a support.

11. The method of enameling tubes which consists in coating the exterior of a plurality of tubes with fluid enamel, connecting the tubes temporarily end to end by connectors, moving the connected tubes hori- 

